[ltt-dev] performance results I measured with the latest lttng patches

[Jiaying Zhang]

Hi Mathieu,

I synced my 2.6.26 lttng code with the latest 0.21 lttng patches
and re-ran the same tbench test. Here are the new results I collected:

lttng-compiled-in, all markers disabled: Throughput 743.931 MB/sec
lttng-compiled-in, default markers enabled, taking an active trace in normal
mode: Throughput 500.24 MB/sec

Compared with the old kernel results:
lttng-compiled-out: Throughput 761.508 MB/sec
lttng-compiled-in, all markers disabled: Throughput 722.983 MB/sec
lttng-compiled-in, default markers enabled, taking an active trace in normal
mode: Throughput 636.569 MB/sec

Looks like the latest changes do help to improve the performance when lttng
is compiled in but tracing is disabled. However, just enabling lttng
configuration
options still adds 2~3% overhead. This is still too high for us. Our
expectation
is that compiling lttng into kernel should add very little overhead when no
trace
is taken.

Another observation is that the new changes seem to slow down the tracing
performance a lot. I haven't dig into the code to see where the overhead
comes
from. Have you measured the latest lttng performance with any benchmark?
If so, do you mind sharing your results and test configurations?

Thanks a lot!

Jiaying
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